From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Improving engine power output and speed by modifying camshaft timings and design for the J.1 and Phantom II models.
| Identifier | ExFiles\Box 102\5\ scan0143 | |
| Date | 10th October 1932 | |
| -2- Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}5/KT.10.10.32. On J.1, however, we have a definite opportunity of getting a better top power output with a reduced toe cam having a longer duration. We attach a curve shewing how we pick up low speed M.E.P. by increasing the tappet clearance on a shaft of this type, and we think the earlier of the two timings given is really a good compromise. It corresponds closely to the present P.II. timing. Two cams to form E.57175. Valve lift curve Sch.1543. [Diagram 1: BEST J.1 CAMSHAFT with labels EX, IN, .010, 50, 40] [Diagram 2: NEW STANDARD P.II CAMSHAFT with labels 24, 1.5, EX, IN, .010, 52, 44] We think that if we use Peregrine toe on J.1 the worst that can happen is a slight warming up tappet period which will not be as bad as the P.II is at present. On the other hand, with the longer duration shaft we shall be able to run the engine up to 4500 r.p.m. and maintain power, which will enable us to gear lower, get better acceleration, and yet shew good M.P.H. top speed. We shall want the new distributor with the double contact breaker on J.1. We think the short toed cam is essential on this engine to save the exhaust valves. Hs{Lord Ernest Hives - Chair}/an. | ||